Refinement of a process of manufacturing semiconductor memory elements (e.g., NAND flash memories) increases applications of the semiconductor memory elements. In particular, in an enterprise field, such as of servers, the number of cases of adopting semiconductor memory devices (e.g., SSDs (Solid State Drives)) including semiconductor memory elements, instead of HDDs (Hard Disk Drives), has been increasing.
An SSD is internally equipped with multiple semiconductor memory elements, and achieves write and read (I/O processes) of a large amount of data in a short period of time through controlling the semiconductor memory elements in parallel (e.g., PTL 1).